Nah, he means when you have like yours 12v1 19a, 12v2 19a, 12v3 19a, that you can't do a math like 3x19A, so i have 57Amps ! It doesn't work like that, but you didn't say that, you said 40A and i think thats pretty safe. ( you have that from the psu i guess ? )
So yeah...here is what I deduced...tell me if I'm wrong.
The PSU says +12V1, 12V2,12V3 maximum output 624 Watts max....SO 624w/12v=52A.
The GPU says 24A but I think the GPU amp rating is total system amps not what it will draw itself. So I think I'm good to go. Man I love learning something new!